Update contribution documentation
Update contribution documentation

Remove mention of the develop branch since it's going away in favor of a much
simpler branching model (feature branches off master).  The use of git-flow was
a great learning experience, but is really too much for projects such as this.

aparente/Dotfiles,Bklyn/dotfiles,aparente/Dotfiles,nilehmann/dotfiles-1,aparente/Dotfiles,aparente/Dotfiles